1. Field of the Invention
This invention relates to shaft seals, also known as oil seals, designed for sealing against fluid leakage along shafts, such as engine crankshafts and motor vehicle drive transmission shafts, and more particularly to shaft seals of the type having thereon bi-directional pumping elements, such as ridges or grooves, for feeding back to the sealing lip (regardless of the direction of rotation of the shaft), any oil or other fluid tending to leak past the sealing lip. 2. Description of the Prior Art
It is known to seal shafts by means of shaft seals having pumping elements (helical ridges or grooves) on the shaft or sealing element surface for feeding back to the sealing lip oil or other fluid tending to leak past the sealing lip. It is also known to mold such ridges or grooves into an elastomeric sealing element using oppositely directed ridges or grooves which meet the sealing lip at a small angle for feeding back oil in either direction of shaft rotation.
It is an object of the present invention to provide a method for making a bi-directional hydrodynamic shaft seal having a sealing element made from non-elastomeric material with helical or elliptically shaped pumping elements such as ridges and grooves which meet the sealing lip at a small angle for feeding back oil or other fluid in either direction of shaft rotation.
It is a further object of the present invention to provide a method for making the pumping elements on the non-elastomeric member by forming on the non-elastomeric member, while it is in the flat state as a ring or disc, a series of pumping elements, either ridges or grooves, in the shape of non-concentric circles, and then forming at least a portion of the non-elastomeric ring or disc into a conical shape such that the circular pumping elements become helical or elliptically shaped bi-directional pumping elements.